1. Field of the Invention
The present invention relates to a plate type reformer and a fuel cell system including the reformer, and more particularly, to a plate type reformer and a fuel cell system including the reformer, in which a heat of reaction in a combustion reactor is used to generate hydrogen gas, thereby enhancing reaction efficiency and thermal efficiency.
2. Description of the Related Art
A fuel cell is a power generation system that directly changes chemical reaction energy due to a reaction between hydrogen and oxygen into electrical energy, in which the hydrogen is contained in a hydro carbonaceous material such as methanol, ethanol, natural gas or the like.
The fuel cell is classified into a phosphate fuel cell, a molten carbonate fuel cell, a solid oxide fuel cell, a polymer electrolyte membrane fuel cell, an alkaline fuel cell, or etc. according to the kinds of electrolyte. Such fuel cells are operated on basically the same principle, but differ in the kind of fuel, the driving temperature, the catalyst, and the electrolyte, etc. from one another.
Among these fuel cells, the Polymer Electrolyte Membrane Fuel Cell (PEMFC) has advantages as compared with other fuel cells in that its output performance is excellent; its operation temperature is low; its start and response are quickly performed; and it can be widely used as a portable power source for an automobile, a distributed power source for a house and public places, a micro power source for electronic devices, etc.
The PEMFC includes a stack, a reformer, a fuel tank, and a fuel pump. The stack forms a main body of the fuel cell, and the fuel pump supplies fuel from the fuel tank to the reformer. The reformer reforms the fuel to generate hydrogen gas, and supplies the hydrogen gas to the stack. Thus, in the PEMFC, the fuel pump supplies the fuel from the fuel tank to the reformer, the reformer reforms the fuel to generate the hydrogen gas, and the stack electrochemically reacts the hydrogen gas with oxygen gas, thereby generating electrical energy.
In the foregoing fuel cell system, the stack has a structure in which several or dozens of unit cells including a Membrane Electrode Assembly (MEA) and a separator closely-contacting the opposite sides of the MEA are stacked. The MEA has a structure in which an anode and a cathode are attached with an electrolyte membrane therebetween. Furthermore, the separator, which is generally called a bipolar plate by those skilled in the art, is employed not only as a passage for separating the MEA and supplying the hydrogen gas and the oxygen gas needed for reaction of the fuel cell to the anode and the cathode of the MEA, but also as a conductor to electrically connect the anode and cathode of the MEA in series. Therefore, the hydrogen gas and the oxygen gas are respectively supplied to the anode and the cathode through the separator. In this process, the hydrogen gas is oxidized in the anode, and the oxygen gas is reduced in the cathode, so that electrical energy is generated as electrons generated at this time are moved, concomitantly generating heat and water.
The reformer is a device employing chemical catalytic reaction due to the heat energy to generate the hydrogen gas from the fuel containing hydrogen. In general, the reformer includes a combustion reactor to generate the heat energy, a reforming reactor to generate the hydrogen gas from the fuel using the heat energy, and a carbon monoxide eliminator to decrease the concentration of carbon monoxide contained in the hydrogen gas.
However, in the conventional reformer, the combustion reactor and the reforming reactor are placed separately from each other, so that the heat generated in the combustion reactor is transferred to the reforming reactor. Because the heat exchange is not directly performed between the combustion reactor and the reforming reactor of the conventional reformer, it takes relatively long time to preheat the reforming reactor, a heat-transferring path is relatively long, and so on. Thus, the conventional reformer has poor thermal efficiency.
Furthermore, because the combustion reactor and the reforming reactor of the conventional reformer are separately provided, there is a limit to reducing the size of the fuel cell system.
Also, the conventional fuel cell system separately preheats the fuel, which is supplied to the reformer at an initial starting, so that the energy must be consumed in preheating the fuel. Therefore, the performance efficiency of the fuel cell system is lowered.